1. Technical Field
Example embodiments of the present invention relate in general to a mobile communication system, and more specifically, to a method of deciding a radio link failure at a base station in a mobile communication system.
2. Related Art
A radio link failure refers to a situation in which an unexpected delay or discontinuity occurs in a radio bearer providing a service due to a signal propagation condition inappropriate to a radio environment between a user terminal and a base station, a system malfunction, or the like.
Appropriate detection of the radio link failure is an important factor for rapidly re-establishing a radio connection and providing a user with high service fidelity.
In particular, when a radio link status between a terminal and a base station is not smooth, since the terminal has to be handed over to another base station through a radio resource control (RRC) entity after detection of the radio link failure, detection of the radio link failure is an important factor for guaranteeing service fidelity. For example, when the terminal enters a coverage hole, or the like, it is important to rapidly detect the radio link failure and hand over the terminal to an appropriate target cell so as to minimize a call drop.
Typically, the radio link failure is detected based on the channel quality measured in a physical layer of a terminal or a base station. Generally, since the measurement of the channel quality in the physical layer of the terminal is performed in a downlink, it is more accurate for the base station, which can collect both the uplink channel quality and the downlink channel quality, to estimate a radio link status based on measurement of the channel quality.
The base station measures the downlink channel quality based on a channel quality indicator (CQI) fed back through a physical uplink shared channel (PUSCH) or the physical uplink control channel (PUCCH). However, when the uplink channel quality is bad, it is difficult to expect the accuracy of the downlink CQI information fed back through the uplink channel.